Traffic marking



United States Patent 3,450,556 TRAFFIC MARKING Milton R. Radcliffe, Marblehead, and Charles G. Newton, Jr., Beverly, Mass., assignors to United Shoe Machinery Corporation, Flemington, N.J., and Boston, Mass., a corporation of New Jersey No Drawing. Filed June 24, 1965, Ser. No. 466,801

Int. Cl. B4411 1/48 US. Cl. 117-62 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to trafiic marking and specifically traffic marking adapted for temporary use.

Traffic marking, based on paints and other organic polymer coating systems, has broad acceptance. It is used on highways, air strips, and other traflic :areas for the purpose of designating tratfic fiow patterns to be followed relative to the particular area. While this expedient has contributed greatly to safety in facilitating safe and expeditious flow of traflic, there is one aspect of this where hazards have actually been created and, continue to exist. This involves situations where, after providing the marking, it is decided to redirect or change the flow of tratfic. This may be done to carry out repairs on the traffic area surface or relocate or redirect the area, etc. In those situations, rather than physically remove the markings, it has been the practice to paint over the markings, which are generally white or yellow lines, symbols, etc., and, by doing so, obliterate the original marking. In doing this an overmarking, for example, a paint, is used having a coloration diiferent from that of the original marking, and one which approaches that of the trafiic area surface which may be pavement or other topping or surfacing material. With trafiic use continuing, however, the overmarking becomes worn down exposing the original trafiic marking, which then creates a considerable traflic hazard.

It is an object of this invention to provide a traffic marking system adapted for temporary use, which contributes to improved trafiic safety.

This and other objects of the invention are attained in the use of a trafiic marking composition the initial coloration of which is capable of being conveniently and effectively obliterated. The trafiic marking composition comprises (a) a light colored pigment capable of color discharge to or approaching an appropriate background color when exposed to sulfide ion under basic or alkaline conditions and (b) a vehicle for the pigment which includes Ian alkaline-sensitive organic polymeric material.

The light colored pigments for use in the trafiic marking composition used in this invention are preferably white and yellow in coloration; they are lead and antimony compounds. Specifically, these include the lead oxides, lead hydroxides, lead carbonates, which provide white coloration, the lead chromates which provide yellow coloration and antimony oxide which provides a white coloration. These pigments are capable of color discharge or of being permanently discolored to a black, dark brown, grey or other non-spectacular coloration when exposed to sulfide ion under alkaline conditions. These ice pigments may be used in regular pigment amounts and may be neutral or basic pigments, with the basic pigments being preferred for the reason that they undergo color discharge under milder conditions. Other pigments and colorants in tinting amounts may be used in con junction with the lead and antimony pigments indicated. When tinting pigments are included they should be such that they will not interfere to any significant extent with the attainment of a desirable background color, on later treatment with sulfide ion.

The vehicle for use in the trafiic marking composition used in this invention includes an alkaline-sensitive organic polymer material. The alkaline sensitivity is designed to facilitate dispersion of the sulfide ion throughout the composition, and as a result obtain cplor discharge throughout the composition mass. The alkaline sensitivity may be an intrinsic property of the polymer material, that is it may result from a monomeric moiety or unit from which the polymer is produced, or it may be the extrinsic property, that is it may result from an adjunct material included or admixed with the polymer on which the polymer material is based. Of these the intrinsic type is preferred. Various synthetic organic polymers, copolymers, interpolymers and polymer blends may be used for this purpose. These are exemplified by styrenemaleic anhydride copolymers, vinyl acetate-acrylic acid copolymer, vinyl acetate-maleic acid copolymers and a number of other acid monomer-based polymers. It is also possible to use natural organic polymers such as the various natural resins as well for this purpose. These are less desirable for the purpose than synthetic organic polymers. The polymers may be used singularly or in admixture with other natural or synthetic polymer materials as part of the vehicle. These other polymeric materials may be blended or mixed with some limitation as to amount, with the alkaline-sensitive polymer materials in order to contribute various improvements in physical properties to the composition. Illustrative of this, a high styrene content synthetic rubber may be included in order to provide the trafiic marking composition with increased toughness and wear resistance. Other polymeric materials which may be included are chlorinated rubber and polyvinyl chloride to provide the composition with improved adhesion and weathering properties.

The vehicle for use in the traffic [marking composition may include various paint and coating extenders and ap plication adjuncts such as typical paint thinner compositions or aqueous emulsions designed to provide desired application properties and drying time to the compositions. In addition to that it may also be desirable to include various plasticizers, ultraviolet absorbers, also abrasive resistance improving agents and adhesion improving agents, etc. in addition to those of a polymeric nature; also reflecting beads, particles, etc. These materials should also be chosen so as not to interfere significantly with the penetration of the sulfide ion into the composition, nor with its ability to react with the pigment to the extent required to effect color discharge.

The traffic marking composition of this invention is efiectively eradicated at a determined time by exposing it to a sulfide ion under alkaline conditions, preferably at a pH ranging about 9.0 to 14.0. In one manner for doing this a color discharging solution which is a water solution of a sulfide ion containing compound, such as sodium sulfide, is used. A concentration of 2 to 20 percent by weight of the sulfide ion containing compound, such as the sodium sulfide, provides a solution which operates well under ambient temperature conditions to effect color discharge of the pigment. Variation in the concentration may be expected. This will be dependent upon a number of factors such as the particular pigment and vehicle used,

EXAMPLE I A. Preparation of traffic marking compositions (1)A water-based traffic marking composition is prepared from the following materials.

Material: Parts by wt. (a) Methocel, 1500 cps. (3 percent solution of methyl cellulose in water) 250 (12) Sodium dodecyl sulfosuccinate 4 (c) Ethylene glycol 36 (d) White lead (basic lead carbonate) 500 (e) Vinyl acetate maleic anhydride copolymer 1568 (f) Butyl benzyl phthalate 224 Materials a-d are mixed together in a paddle-type mixer and then given two passes through a paint mill to effect dispersion of the pigment throughout the mix. The mix is then charged into a propeller-type mixer having the copolymer already present. Stirring is carried out for a period of 15 minutes at a speed which avoids vortex formation. The butyl benzyl phthalate is then added slowly over a period of 5 minutes. The composition obtained, which has a white coloration, and a viscosity of 8000 cps., is stored in a tightly covered container until use.

(2) The procedure set forth in paragraph 1 above is again repeated except that the pigment used is medium chrome yellow (basic lead chromate). The composition obtained has a yellow coloration and a viscosity of 9200 cps.

(3) The procedure set forth in paragraph 1 above is again repeated except that the pigment used is antimony oxide. The composition obtained has a white coloration and viscosity of 6400 cps.

B. Preparation of color discharging solution (1) A color discharging solution is prepared using the following materials.

Material: Parts by wt. (a) Sodium sulfide 40 (b) Water 1560 The materials are stirred together until the sodium sulfide is dissolved to provide a 2.5% by weight solution of sodium sulfide in water.

C. Testing of traffic marking compositions and method of obliterating the same The compositions produced in paragraph A above are applied as marking stripes feet in length and 1.0 foot wide onto an asphalt-aggregate paved surface having a vehicle usage estimated at about 1500 passes per day. After a period of thirty days at which time only small wear is evident, the compositions are treated with the sodium sulfide color discharging solution, prepared according to paragraph B above. The solution is applied by reed bristle brush at ambient temperature condition (65 F.) and allowed to stand for a period of 7 to 10 minutes. As the point it is noted that the colorations (white and yellow) have discharged to a dark grey in the case of the white and a brownish grey in the case of the yellow; all are difficult to discern or differentiate from the asphalt background paved surface at a distance of more than a few feet. Traffic is then allowed to resume. The colordischarged stripes are then checked at time intervals extending over six months. At each check the color of the obliterated stripes has not changed, indicating that the initial color-discharging took effect throughout the compositions. At the six month check it is noted that the compositions are essentially dissipated, or are no longer distinguishable from the pavement background.

It will thus be seen that the objects set forth above, among those made apparent from the preceding descrip tion, are effectively obtained, and since certain changes may be made in the above trafiic marking compositions and method of obliterating the same without departing from the scope of the invention, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

Having thus described our invention what we claim as new and desire to secure by Letters Patent of the United States is:

1. A method for providing temporary traffic marking which comprises the steps of applying a traffic marking composition to an area of dark coloration to be marked, the said composition comprising (a) a pigment of light coloration capable of color discharge to a dark coloration when exposed to sulfide ion under alkaline conditions and (b) a vehicle for the pigment which includes an organic polymer material penetrable by sulfide ion under alkaline conditions, and, thereafter contacting the composition with an alkaline, sulfide ion-containing solution to color discharge the pigment to a dark coloration.

2. A method according to claim 1 wherein the pigment is selected from the class consisting of lead carbonnates, lead chromates, lead hydroxides, lead oxides and antimony oxide.

3. A method according to claim 1 wherein the alkaline, sulfide ion-containing solution has a pH of about 9 to 14.

4. A method according to claim 3 wherein the solution is an aqueous solution of sodium sulfide.

5. A method according to claim 4 wherein the solution is made up from 2 to 20 percent by weight of sodium sulfide.

References Cited UNITED STATES PATENTS 3/1952 Steiner l06-22 5/1966 De Vries 941.5

OTHER REFERENCES ALFRED L. LEAVITT, Primary Examiner.

I. A. BELL, Assistant Examiner.

US. Cl. X.R. 94-15 

